1. Field of the Invention
This invention relates to a disc cartridge having a disc-shaped recording medium, such as a magnetic disc, accommodated therein.
2. Description of Related Art
There has so far been known a disc cartridge having a flexible magnetic disc with a diameter of, for example, 3.5 inch, accommodated therein as a disc-shaped recording medium. This disc cartridge has a main cartridge body portion including a set of shells, that is an upper shell and a lower shell, combined together. These upper and lower shells are formed of a resin material, and are provided with recording and/or reproducing apertures for exposing a portion of the flexible magnetic disc to outside across its inner and outer rims. On the main cartridge body portion is mounted a shutter member for opening/closing the recording and/or reproducing apertures. Within the main cartridge body unit, there are provided an upper liner sheet and a lower liner sheet, forming a liner sheet set, for protecting the flexible magnetic disc. These upper and lower liner sheets are welded and bonded to the inner surfaces of the upper and lower shells.
In the conventional disc cartridge of the above-described type, a shutter member is moved on loading the disc cartridge in a recording and/or reproducing apparatus so that its recording and/or reproducing aperture is opened. As the flexible magnetic disc is run in rotation, the information is recorded and/or reproduced by a magnetic head intruded through the recording and/or reproducing aperture.
Recently, in a portable electronic equipment, such as a portable computer or a digital still camera, a demand is raised for a recording and/or reproducing apparatus that is able to handle the information of a larger volume, and for a information recording medium used for this recording and/or reproducing apparatus.
As for an information recording medium, used for this sort of the recording and/or reproducing apparatus, it is proposed to reduce the size or thickness of a disc cartridge having the flexible magnetic disc housed therein.
Meanwhile, if it is desired in the above-mentioned conventional disc cartridge to reduce the size or thickness of the main cartridge body portion, it is retained to be difficult to realize a reduced thickness because the main cartridge body unit is formed of synthetic resin. It is necessary to maintain the thickness of the disc cartridge of the order of 0.3 mm at a minimum even if importance is not attached to the mechanical strength or deformation such as warping of the major surfaces of the upper or lower shell.
If it is necessary to secure the mechanical strength of the main cartridge body portion, it is necessary to increase the thickness of the upper and lower shells further, so that a problem is presented that it is extremely difficult to fabricate the main cartridge body unit designed to cope with a flexible magnetic disc with a thickness of the order of 2 inch solely from a resin material.
In order to reduce the thicknesses of the upper and lower shells of the main cartridge body unit, it may be contemplated to form the upper and lower shells from a metallic material.
In this disc cartridge, it is necessary to provide upper and lower liner sheets for protecting the flexible magnetic disc. However, since it is impossible to weld the upper and lower shells of metal, it is difficult to bond the upper and lower liner sheets to the inner surfaces of the upper and lower shells of metal.
It is therefore an object of the present invention to provide a disc cartridge in which the main cartridge body unit can be reduced in size and thickness and in which the disc-shaped recording medium can be protected reliably.
For accomplishing the above object, the present invention provides a disc cartridge including a disc-shaped recording medium, a main cartridge body unit including an upper plate and a lower plate, both of a metal material, forming a plate pair, and an intermediate frame, sandwiched between the upper and lower plates, and a set of protective members bonded to inner surfaces of the upper and lower plates for protecting the disc-shaped recording medium. The disc-shaped recording medium is accommodated in the main cartridge body unit.
In the present disc cartridge, in which a set of protective members are bonded to the inner surfaces of the upper and lower plates via adhesive layers, the protective members may be provided readily.